Method of assembling electric insulators



FIG 2 INVENTOR 02770 G. GEM/and BY ATTORNEY Nov. 1, 1938. o. G. CALLAND- METHOD OF ASSEMBLING ELECTRIC INSULATORS Filed Dec. 27, 1937 FIG.4'

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Patented Nov. 1, 1938 UNITED STATES PATENT OFFICE METHOD OF ASSEMBLING ELECTRIC INSU- LATORS Application December 27, 1937, Serial No. 181,939

3 Claims.

This invention relates to electric insulators and particularly to a method of assembling the parts of suspension insulators so as to fix the position of the exposed surface of the connecting cement.

One object of the invention is to prevent electric discharges from the surface of the cement.

Another object of the invention is to facilitate the assembly of the parts in proper relation to one another without deposit of excess cement upon the finished insulator.

A further object of invention is to provide an improved method of assembling insulator parts which will result in a better product.

Other objects and advantages will appear from the following description;

The invention is exemplified by the combination and arrangement of parts and by the steps of the process described in the following specification and illustrated in the accompanying drawing, and it is more particularly pointed out in the appended claims.

In the drawing:

Fig. 1 is an elevation with parts in section showing one step in the process of assembling insulators according to the present invention.

Fig. 2 is a fragmentary section of an insulator showing the relation of the parts after assembly.

Fig. 3 is an elevation and Fig. 4 is a section of a filler or packing washer used in assembling the insulator.

In the manufacture of certain types of porcelain insulators, it has been the practice heretofore to form a porcelain body having a flange and a projection or head at one side of the flange, which head is secured in a metal cap by means of cement. Because of slight irregularities in the cap and porcelain, it is not practical to determine exactly how much cement will be required to fill the space between the connected parts. The practice heretofore has been to deposit, in the inverted cap, a slight excess of cement which is forced out about the rim of the cap when the head of the porcelain is inserted. This excess of cement is removed as completely as possible, but the operation leaves a somewhat irregular edge of cement at the rim of the cap. The cement is slightly conductive of electricity and when the finished insulator is subjected to the voltage of a transmission line, discharge streamers are apt to form on the irregular, projecting portions of the cement giving rise to radio disturbances and other objectionable effects. In order to avoid this objection, applicant has devised a method of assembly, illustrated in the accompanying drawing, in which the numeral l designates the cap of a suspension insulator into which the head ll of a dielectric member is inserted and secured by cement l2. Before the parts are assembled, a Washer l3 of fibre, heavy pasteboard or other suitable material is disposed over the head II. The inner edge of the washer is previously turned to one side as illustrated at M so that it projects laterally, relative to the plane of the body of the washer. The washer is of such thickness that when the parts are assembled as shown in Fig. 1, the laterally turned inner edge will substantially fill the space between the rim of the cap in and the head of the insulator. After the washer i3 is in place, the cap is inverted and a slight excess of cement placed inside the cap, after which the head is pressed into the opening in the cap forcing out the excess of cement between the rim of the cap and the exposed surface of the washer. As the parts are brought firmly together, the entire excess of cement will be forced out and the rim of the cap will finally be brought to bear firmly upon the upper surface of the washer and the outer surface of its upturned inner edge, so that the space occupied by the cement will be completely closed and the cement will be excluded from the space occupied by the upturned edge of the washer. After the cement has hardened, the washer can be readily removed and the space occupied by the upturned edge I 4 will be completely clear of cement. A properly formed tool with a bent point may be used for removing the upturned edge of the washer if this is found necessary. After the washer is removed, the space at the lower edge of the cap will have the appearance shown in Fig. 2, in which the cement l2 will terminate back of the lower edge of the cap, leaving the space shown at l5 unoccupied. This will leave a smooth edge at the extremity of the cement, but what is of more importance, the cement will terminate back of the caprim so that the slightly projecting portion l6 of the cap will act as an electrostatic screen to prevent formation of corona from the cement even if there should be rough places on the edge of the cement. The cap being formed of metal can be given a nicely rounded extremity to prevent formation of corona from the edge of the cap.

It has been found in practice that this process provides an easy method of assembling the parts and results in an insulator which is uniformly silent in operation so far as the formation of corona at the edge of the cap is concerned. Applicant is aware that Washers have heretofore been placed beneath the edge of the cap of suspension insulators, but so far as applicant knows they have never been formed so as to extend into the space between the rim of the cap and the head of the insulator, so that heretofore no method of assembling has ever been used, to applicants knowledge, which uniformly locates the edge of the cement back of the extremity of the cap. Wherever the cement is permitted to extend to a position adjacent the edge of the cap, as is the case when a flat washer is used, streamers will form from the rough edge of the cement, but by turning up the inner edge of the washer so as to insure termination of the cement back of the edge of the cap, applicant provides an electrostatic screen for the edge of the cement which has been found in practice to eliminate the formation of corona at this point.

I claim:

1. The method of assembling an insulator comprising the steps of introducing cement into an opening in a metal fitting, applying packing material to a dielectric member in position to fill the space within said fitting immediately adjacent the extremity of said fitting when said dielectric member is inserted into said opening, inserting said dielectric member into said opening and said packing material into the space within said opening immediately adjacent the extremity of said fitting and subsequently removing said packing material to leave a clear space about said dielectric member within said opening adjacent the termination of said fitting, said space being deep enough that the projecting edge of said fitting forms an electrostatic screen to prevent electrical discharge from the termination of said cement.

2. The method of assembling a suspension insulator comprising a cap and a dielectric memher having a flange and a head portion, said method comprising the steps of applying packing to said insulator about said head portion adjacent said flange in position to extend into said can when said insulator is assembled and assembling said dielectric member and cap with cement interposed between the adjacent surfaces thereof, the cement being excluded from the space within said cap immediately adjacent the rim of said cap by said packing permitting the cement to harden and subsequently removing said packing to leave an open space within said cap of sufiicient depth that the projecting rim of said cap provides an electrostatic screen to prevent electric discharge from the surface of said cement.

3. The method of assembling a dielectric member and a metal cap comprising the steps of forming a washer of packing material, turning the inner edge of said Washer laterally relative to the plane of the body of said Washer, disposing said washer about the dielectric member with said turned edge encircling said member and assembling said dielectric member and cap with cement interposed between adjacent surfaces thereof so that the rim of said cap surrounds the laterally turned edge of said washer and so that said edge excludes the cement from the space within said cap between said dielectric member and cap adjacent said rim permitting said cement to harden and thereafter removing said washer including the laterally turned edge thereof to provide an open space within said cap about said dielectric member of sufiicient depth that the projecting rim of said cap forms an electrostatic screen to prevent discharge from the surface of said cement.

OTHO G. CALLAND. 

